Rootworms are on the move

Though it happened a little later than normal, entomologists report discovering freshly hatched larvae of the western corn rootworm late last week in Indiana, showing that the pest could become a problem of economic proportions later this growing season.

Purdue University entomologists Christian Krupke, John Obermeyer and Larry Bledsoe discovered the larvae -- the first of the year -- last Thursday, June 6, and they believe they'd hatched just 2 days prior, says University of Illinois Extension crop scientist Mike Gray. One noteworthy thing about their discovery is it's later than normal; it's even later than current growing-degree day (GDD) accumulations would dictate.

"This event was a little later than heat-unit totals predicted," Gray says. "I suspect that the drought of 2012 forced much deeper egg laying in the soil contributing to the slightly later hatch this spring."

But, even though they're likely coming late, in theory, because of last year's drought, don't sit back and wait for them, Gray advises. That's especially true when it comes to watching for rootworm damage, which could come in the normal time window despite the bug's generally late start.

"Not all corn rootworm larvae hatch at once. This staggered event will occur over the next several weeks," Gray says. "By late June and early July, we should begin to see evidence of root injury, especially in fields where corn rootworm products may not be performing up to acceptable standards."